Compressed gases have conventionally been shipped in cylindrical containers having a valve assembly disposed within a neck portion of the container to regulate the flow of gas from the container. In the prior art, to prevent damage to the valve assembly during transit, protective caps have been inserted over the neck of the container so that the valve assembly is safely enclosed within the protective caps. Openings have been provided through the sidewall of the protective caps in order to prevent a possible pressure build-up of compressed gas within the protective cap. If, for example, the valve assembly develops a leak during transit, the leaking gas is simply vented to the atmosphere through the opening through the protective cap.
It is known that even routine handling of the gas cylinders can occasionally result in the leakage of gas from the valve assembly. Through handling and shipment of the cylinders, it is possible for a valve assembly to loosen in the neck of the cylinder or for the valve seat to be opened slightly by vibration or otherwise become damaged producing a small gas leak from the gas cylinder. Although the occasional or even sporadic leakage of relatively innocuous gases from a cylinder can be tolerated, a severe health hazzard may result when the leakage of highly toxic gases, such as arsine and phosphine, occur creating a greater concern. One factor contributing to the concern is that the rapid expansion of the electronics industry has resulted in a sharp increase in the shipment of highly toxic gases of the types mentioned above used in the manufacture of semiconductor devices.
If a leakage of a highly toxic gas develops from a conventional gas cylinder during transit, the leaking cylinder must be immediately isolated to prevent possible exposure of human beings to the toxic gas. Once the leaking container is secured in an isolated environment, trained personnel and safety equipment must be immediately transported to the location of the gas cylinder in order to detoxify, confine or collect the leaking gas. Since time delays often occur in transporting the requisite personnel and safety equipment to the location of the leaking cylinder, significant health risks could be involved. As a result, the transportation and shipment of compressed gases of a highly toxic nature necessitates the implementation of special handling procedures and safety precautions. Since small amounts of a toxic gas, such as arsine, can be extremely lethal, it is of the utmost importance to prevent the possible leakage of toxic gases from their pressurized shipping containers.
In accordance with the present invention, a sealable fluid containment assembly is provided which effectively and efficiently prevents the possible leakage of compressed gas from a base container such as a gas cylinder. The assembly in accordance with the present invention functions to hermetically seal the base container and relieve stresses at a neck portion of the base container which may be produced by external forces on the neck portion or valve assembly resulting, for example, from inadvertent dropping or mishandling of the container.